Thermoplastic polymer powder

ABSTRACT

A thermoplastic polymer powder which (i) consists mainly of an acrylic block copolymer comprising one or more acrylic ester polymer blocks (A) and bonded thereto at least one polymer block selected among methacrylic ester polymer blocks (B) and acrylic ester polymer blocks (C) differing in structure from the blocks (A); (ii) has a complex dynamic viscosity η*(5) of 5.0×10 3  Pa.s or lower as measured under the conditions of a temperature of 250° C. and an oscillation frequency of 5 rad/sec; (iii) has a Newtonian viscosity index n represented by the equation n=log η*(5)-log η*(50) [wherein η*(5) and η*(50) indicate the complex dynamic viscosities (unit, Pa.s) as measured under the conditions of a temperature of 250° C. and oscillation frequencies of 5 and 50 rad/sec, respectively] of 0.50 or smaller; and (iv) has an average particle diameter of 1 mm or smaller. The thermoplastic polymer powder is suitable for use in molding techniques employing a powder, such as slush molding and in powder coating. A molding, skin material, and the like which are excellent in weatherability, flexibility, mechanical strength, low-temperature properties, adhesion to polar resins, rubber elasticity, safety, etc. can be smoothly produced from the powder.

TECHNICAL FIELD

The present invention relates to a thermoplastic polymer powder, amolded product produced by use of the same, and a process for producingthe molded product. More specifically, the present invention relates toa thermoplastic polymer powder which can be used suitably for moldingtechniques and coating techniques employing a powder, such as slushmolding, rotational molding, powder flame spraying, extrusion molding,calendaring, compression molding and powder coating, a molded productproduced by use of the same, and a process for producing the moldedproduct. When the thermoplastic polymer powder of the present inventionis used to perform any one of the above-mentioned molding and coatingtechniques, it is possible to produce smoothly a molded product, a skinmaterial, a painted film, a composite product having the skin materialor painted film, and so on which cause a lower degree of environmentalpollution based on halogen or the like, have good safety, and arefurther excellent in weatherability, flexibility, mechanical strength,low-temperature properties, adhesion to polar resins, rubber elasticity,and other properties.

BACKGROUND ART

Skin materials produced by use of a soft polyvinyl chloride resincomposition are inexpensive and excellent in flexibility and scratchresistance. Therefore, the skin materials have widely been used hithertoin fields of automobile interior members such as instrument panels, doortrims, console boxes and seats, furniture such as sofas and chairs, andso on. At the time of producing these skin materials, there has beenpopularly used slush molding, wherein a powdery polyvinyl chloride resincomposition is stuck onto the surface of a mold having a complicatedshape and then the composition is heated and molded, in the prior art.Since soft polyvinyl chloride resin powder is inexpensive and excellentin flexibility and can be fashioned into a complicated shape, the powderhas widely been used also in the production of toys and others byrotational molding.

However, polyvinyl chloride resin generates harmful substances such asdioxin when the resin is incinerated, and further it is suspected that aplasticizer used therein acts as environmental disrupter, carcinogens,or the like. Thus, the resin has problems about environmental pollutionand safety. There are also caused problems, such as bleed-out andfogging resulting from the plasticizer.

In light of the above-mentioned points, investigation has been made inrecent years about the matter that a thermoplastic elastomer which doesnot contain any halogen or any plasticizer is used instead of polyvinylchloride resin and the elastomer is subjected to slush molding.

Of molding methods and coating methods using powder, slush molding orrotational molding is performed without applying any fashioningpressure. It is therefore necessary that powdery material stuck onto amold at the time of molding is melted and flows under no appliedpressure so as to form a coating. From this viewpoint, the thermoplasticelastomer powder used in slush molding or rotational molding has arequirement that the melt viscosity thereof is low under low shearing.

As the thermoplastic elastomer powder which is low in melt viscosityunder low shearing, has fluidity even under conditions that nofashioning pressure is applied and further can be applied to slushmolding, there is known a thermoplastic elastomer powder for slushmolding which is made of an elastomer composition of anethylene/α-olefin copolymer rubber and a polyolefin resin (seeJP-A-5-5050). However, the thermoplastic elastomer powder for slushmolding described in the JP-A-5-5050 is a nonpolar resin; therefore, thepowder is low in adhesion to polar resins such as polyurethane resin andABS resin, and thus a composite body or the like which is composed ofthe elastomer and a polar resin is not easily produced. A molded productobtained from this thermoplastic elastomer powder is not sufficientlysatisfactory in flexibility.

As the material for slush molding which exhibits adhesion to polarresins, suggested is a material for slush molding which comprises athermoplastic polyurethane elastomer, a plasticizer, a blockpolyisocyanate, and a pigment (JP-A-11-49948). However, this materialfor slush molding has a problem that the plasticizer, which is used tokeep low-temperature properties, melt fluidity, flexibility and others,causes bleed-out or fogging in the same manner as the flexible polyvinylchloride resin powder, and other problems. This material for slushmolding is also low in weatherability since the base thereof is thepolyurethane elastomer.

An object of the present invention is to provide a thermoplastic polymerpowder which: is good in melt fluidity; can be used suitably for moldingtechniques using powder, such as slush molding and rotational molding,powder coating techniques and the like; does not contain any halogen norany plasticizer; does not cause environmental pollution or anxiety aboutcarcinogenicity; and can be further made into a high-quality moldedproduct, skin material or painted film excellent in weatherability,flexibility, rubber elasticity, low-temperature properties, adhesion topolar resins, texture, external appearances and others.

Another object of the present invention is to provide a molded productobtained from the thermoplastic polymer powder, and a process forproducing the same.

DISCLOSURE OF THE INVENTION

The inventors have repeated eager investigation in order to attain theabove-mentioned objects. As a result, it has been found out that athermoplastic polymer powder which is made mainly of an acrylic blockcopolymer having a specific block structure and further has specificdynamic viscosity properties is good in melt fluidity, and can be usedsuitably for various molding techniques employing powder, such as slushmolding and rotational molding, and powder coating technique. It hasbeen found out that the molded product, skin material, painted film andthe like that are obtained by use of the thermoplastic polymer powdercause no anxiety of environmental pollution and further have excellentsafety since they do not contain any halogen or any plasticizer, andthat they are excellent in weatherability, flexibility, rubberelasticity, low-temperature properties, adhesion to polar resins,texture, external appearances and others.

An acrylic polymer powder which can be used suitably for moldingtechniques using powder, such as slush molding and rotational molding,and powder coating, and which gives a molded product, a skin material, apainted film or some other product that is excellent in flexibility,rubber elasticity, weatherability, low-temperature properties, textureand others by the molding techniques or coating technique has not beenknown in the prior art; and has been unprecedentedly found out by theinventors.

Accordingly, the present invention is: (1) a thermoplastic polymerpowder which (i) is made mainly of an acrylic block copolymer (I)comprising one or more polymer blocks (A) made mainly of structuralunits originating from an acrylic ester [referred to as acrylic esterpolymer block(s) (A) hereinafter]; and at least one polymer block bondedthereto and selected from polymer blocks (B) made mainly of structuralunits originating from a methacrylic ester [referred to as methacrylicester polymer blocks (B) hereinafter] and polymer blocks (C) made mainlyof structural units originating from an acrylic ester different fromthat of the acrylic ester polymer block(s) (A) [referred to as acrylicester polymer blocks (C) hereinafter];

(ii) has a complex dynamic viscosity η*(5) of 5.0×10³ Pa.s or less, theviscosity η*(5) being measured under conditions of a temperature of 250°C. and an angular frequency of 5 rad/sec;

(iii) has a Newtonian viscosity index n of 0.50 or less, the Newtonianviscosity index n being represented by the following equation (1):n=log η*(5)-log η*(50)   (1)wherein n represents the Newtonian viscosity index, η*(5) represents thecomplex dynamic viscosity (unit: Pa.s) measured under conditions of atemperature of 250° C. and an angular frequency of 5 rad/sec, and η*(50)represents the complex dynamic viscosity (unit: Pa.s) measured underconditions of a temperature of 250° C. and an angular frequency of 50rad/sec; and

(iv) has an average particle diameter of 1 mm or less.

The present invention is as follows: (2) the thermoplastic polymerpowder according to item (1), wherein the melt viscosity measured with arotary viscometer at 250° C. and a shear rate of 0.2 sec⁻¹ is 3000 Pa.sor less; (3) the thermoplastic polymer powder according to item (1) or(2), which is obtained by an underwater cutting process or a shockpulverizing process; (4) the thermoplastic polymer powder according toany one of items (1) to (3), wherein the weight average molecular weightof the acrylic block copolymer (1) is from 5,000 to 200,000; (5) thethermoplastic polymer powder according to any one of items (1) to (4),wherein the weight average molecular weight of the acrylic ester polymerblock(s) (A) constituting the acrylic block copolymer (I) is from 1,000to 150,000, and the weight average molecular weights of the methacrylicester polymer block(s) (B) and the acrylic ester polymer block(s) (C)are from 2,000 to 50,000; (6) the thermoplastic polymer powder accordingto any one of items (1) to (5), wherein the acrylic block copolymer (I)is a triblock copolymer made of the methacrylic ester polymer block(B)—the acrylic ester polymer block (A)—the methacrylic ester polymerblock (B); (7) the thermoplastic polymer powder according to any one ofitems (1) to (6), wherein the difference between the solubilityparameter a(A) (unit: MPa^(1/2)) of the starting monomer(s) constitutingthe acrylic ester polymer block(s) (A) and the solubility parameter σ(B)or σ(C) (unit: MPa^(1/2)) of the starting monomer(s) constituting themethacrylic ester polymer block(s) (B) or the acrylic ester polymerblock(s) (C) is 2.5 or less; and (8) the thermoplastic polymer powderaccording to any one of items (1) to (7), which is for slush molding orrotational molding.

Furthermore, the present invention is as follows: (9) a process forproducing a molded product by performing slush molding or rotationalmolding by use of the thermoplastic polymer powder according to any oneof items (1) to (8); (10) a molded product produced by use of thethermoplastic polymer powder according to any one of items (1) to (8);(11) the molded product according to item (10), which is a toy memberhaving a JIS-A hardness of 40 to 95; and (12) the molded productaccording to item (10), which is a lighting cover having a JIS-Ahardness of 95 or more.

BEST MODES FOR CARRYING OUT THE INVENTION

The present invention will be described in detail hereinafter.

The thermoplastic polymer powder of the invention is a thermoplasticpowder which is made mainly of the acrylic block copolymer (I) [theabove-mentioned requirement (i)], satisfies the dynamic viscosityproperties prescribed in the above-mentioned (ii) and (iii), and furtherhas an average particle diameter of 1 mm or less [the above-mentionedrequirement (iv)]. As long as the thermoplastic polymer powder of theinvention satisfies the above-mentioned requirements (i) to (iv), thepowder may be a powder made only of the acrylic block copolymer (I) or apowder made of an acrylic block copolymer (I) composition wherein adifferent component (such as a different polymer or an additive) isincorporated into the acrylic block copolymer (I).

The acrylic block copolymer (I) constituting the thermoplastic polymerpowder of the present invention is a block copolymer comprising one ormore acrylic ester polymer blocks (A); and one or more polymer blocksbonded thereto and selected from methacrylic ester polymer blocks (B)and acrylic ester polymer blocks (C), which are different in structurefrom the acrylic ester polymer blocks (A).

In each of the acrylic ester polymer blocks (A) constituting the acrylicblock copolymer (I), the ratio by mole of structural units originatingfrom an acrylic ester to all structural units constituting the polymerblock (A) is preferably 60% or more by mole from the viewpoint offlexibility, and is more preferably from 80 to 100% by mole.

Examples of the acrylic ester, which constitutes the acrylic esterpolymer block (A), include methyl acrylate, ethyl acrylate, n-propylacrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate,sec-butyl acrylate, tert-butyl acrylate, amyl acrylate, isoamylacrylate, n-hexyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate,pentadecyl acrylate, dodecyl acrylate, isobornyl acrylate, phenylacrylate, benzyl acrylate, phenoxyethyl acrylate, 2-hydroxyethylacrylate, 2-methoxyethyl acrylate, glycidyl acrylate, and allylacrylate. The acrylic ester polymer block(s) (A) may be made of one ormore out of these acrylic esters.

It is preferable that the acrylic ester polymer block(s) (A) is made ofone or more out of ethyl acrylate, n-propyl acrylate, isopropylacrylate, n-butyl acrylate, 2-ethylhexyl acrylate, pentadecyl acrylate,dodecyl acrylate, and 2-methoxyethyl acrylate among the above-mentionedesters since the flexibility of the molded product, the skin material,the painted film, and the like that are obtained by use of thethermoplastic polymer powder of the present invention. It is morepreferable that the block(s) (A) is made of one or more out of ethylacrylate, n-propyl acrylate, n-butyl acrylate, and 2-ethylhexylacrylate. It is even more preferable that the block(s) (A) is made ofone or more out of n-butyl and 2-ethylhexyl acrylate.

In each of the methacrylic ester polymer blocks (B), the ratio by moleof structural units originating from a methacrylic ester is 60% or moreby mole from the viewpoint of heat resistance, and is more preferablyfrom 80 to 100% by mole.

Examples of the methacrylic ester, which constitutes the methacrylicester polymer block (B), include methyl methacrylate, ethylmethacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butylmethacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butylmethacrylate, amyl methacrylate, isoamyl methacrylate, n-hexylmethacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate,pentadecyl methacrylate, dodecyl methacrylate, isobornyl methacrylate,phenyl methacrylate, benzyl methacrylate, phenoxyethyl methacrylate,2-hydroxyethyl methacrylate, and. 2-methoxyethyl methacrylate. Themethacrylic ester polymer block(s) (B) may be made of one or more out ofthese methacrylic esters. It is preferable that the methacrylic esterpolymer block(s) (B) is made of one or more out of methyl methacrylate,ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate,tert-butyl methacrylate, cyclohexyl methacrylate, and isobornylmethacrylate among the above-mentioned esters since the heat resistanceof the molded product, the skin material, the painted film, and the likethat are obtained by use of the thermoplastic polymer powder of thepresent invention becomes better. It is particularly preferable that theblock(s) (B) is made of methyl methacrylate.

In each of the acrylic ester polymer blocks (C), which are made ofacrylic ester units different in structure from the acrylic esterpolymer constituting the acrylic ester polymer block(s) (A), the ratioby mole of structural units originating from an acrylic ester ispreferably 60% or more by mole from the viewpoint of heat resistance,and is more preferably from 80 to 100% by mole.

Examples of the acrylic ester, which constitutes the acrylic esterpolymer block (C), include methyl acrylate, ethyl acrylate, n-propylacrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate,sec-butyl acrylate, tert-butyl acrylate, amyl acrylate, isoamylacrylate, n-hexyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate,pentadecyl acrylate, dodecyl acrylate, isobornyl acrylate, phenylacrylate, benzyl acrylate, phenoxyethyl acrylate, 2-hydroxyethylacrylate, 2-methoxyethyl acrylate, glycidyl acrylate, and allylacrylate. The acrylic ester polymer block(s) (C) may be made of one ormore out of these acrylic esters. It is necessary, however, that thestructural units of the acrylic ester polymer block(s) (C) are differentfrom those of the acrylic ester polymer block(s) (A).

If necessary, the acrylic ester polymer block(s) (A), the methacrylicester polymer block(s) (B) and/or the acrylic ester polymer block(s)(C), which constitute the acrylic block copolymer (I), may comprise asmall amount of a structural unit (monomer unit) originating from adifferent monomer as long as properties of each of the polymer blocksare not taken away from. The kind of the different monomer unit whichthe acrylic ester polymer block(s) (A), the methacrylic ester polymerblock(s) (B) and/or the acrylic ester polymer block(s) (C) may compriseis not particularly limited. Examples thereof include structural unitsoriginating from unsaturated carboxylic acids such as methacrylic acid,acrylic acid and maleic anhydride; olefins such as ethylene, propylene,1-butene, isobutylene, and 1-octene; conjugated diene compounds such asbutadiene, isoprene, and myrcene; aromatic vinyl compounds such asstyrene, α-methylstyrene, p-methylstyrene, and m-methylstyrene; andvinyl acetate, vinylpyridine, acrylonitrile, methacrylonitrile, vinylketone, vinyl chloride, vinylidene chloride, vinylidene fluoride,acrylamide, and methacrylamide. One or more out of these monomer unitsmay be contained.

In the acrylic block copolymer (I), the number of bonds between theacrylic ester polymer block(s) (A), and the methacrylic ester polymerblock(s) (B) and/or the acrylic ester polymer block(s) (C), and thestructure of the bonds are not limited if the number and the structuregive the thermoplastic polymer powder satisfying the dynamic viscosityproperties prescribed in the above-mentioned (ii) and (iii). Since themolded product, the skin material, the painted film and the like thatare formed by use of the thermoplastic polymer powder of the presentinvention become better in flexibility, the acrylic block copolymer (I)is preferably a diblock copolymer represented by the following generalformula (1) or a triblock copolymer represented by the following generalformula (2) or (3), and is more preferably a triblock copolymerrepresented by the following general formula (3):A-B   (1),C-A-B   (2), andB-A-B   (3)wherein A represents an acrylic ester polymer block (A), B represents amethacrylic ester polymer block (B), and C represents an acrylic esterpolymer block (C) made of acrylic ester structural units different instructure from the structural units constituting the acrylic esterpolymer block (A).

In the diblock copolymer represented by the general formula (1), thetriblock copolymer represented by the general formula (2), and thetriblock copolymer represented by the general formula (3), it ispreferable that A is an acrylic ester polymer block (A) having a glasstransition temperature of lower than 20° C., B is a methacrylic esterpolymer block (B) having a glass transition temperature of 20° C. orhigher, and C is an acrylic ester polymer block (C) having a glasstransition temperature of 20° C. or higher.

The difference between the solubility parameter σ(A) (unit: MPa^(1/2))of the monomer(s) constituting the acrylic ester polymer block (A) andthe solubility parameter σ(B) or σ(C) of the starting monomer(s)constituting the methacrylic ester polymer block(s) (B). or the acrylicester polymer block(s) (C) is preferably 2.5 or less, more preferably2.0 or less, even more preferably 1.5 or less.

The solubility parameter referred to in the present invention, which maybe referred to as the “SP value” hereinafter, can be calculated by themethod described in “POLYMER HANDBOOK Fourth Edition”, VII, pp. 675-714(published by Wiley Interscience Co. in 1999) and “Polymer Engineeringand Science”, 1974, Vol. 14, pp. 147-154. When the SP values of mainmonomers which are preferably used in the present invention are obtained[the SP values are each described in the following parentheses], theresults are as follows: methyl methacrylate (18.3), n-butyl acrylate(18.0), and 2-ethylhexyl acrylate (17.6).

In general, any block copolymer having polymer blocks wherein monomershaving different SP values are structural units has a micro phaseseparation structure, and exhibits a non-Newtonian viscosity. Even blockcopolymers have no micro phase separation structure (disorder state) toexhibit the Newtonian viscosity if polymer blocks therein are soluble ineach other. In order for the block copolymer in the invention to have alow melt viscosity under low shearing and have fluidity even under noapplied fashioning pressure, it is preferable that the copolymerexhibits the Newtonian viscosity in the state that the copolymer ismelted. When the difference between the SP values of the monomers whichare structural units constituting the respective polymer blocks issmall, the order/disorder transition temperature of the block copolymercan be made low so that the block copolymer can be favorably moldedwithin the temperature range that the copolymer exhibits the Newtonianviscosity. On the other hand, if the difference between the SP values ofthe monomers which are structural units constituting the respectivepolymer blocks is large, the order/disorder transition temperature ofthe block copolymer tends to become higher than the decompositiontemperature of the block copolymer so that the copolymer is notunfavorably molded with ease at a temperature that the copolymer isturned into a disorder state.

Specific and preferable examples of the acrylic block copolymer (I)include diblock copolymers such as [poly(n-butyl acrylate)]-[poly(methylmethacrylate)] and [poly(2-ethylhexyl acrylate)]-[poly(methylmethacrylate)]; and triblock copolymers such as [poly(methylacrylate)]-[poly(n-butyl acrylate)-[poly(methyl acrylate)], [poly(methylacrylate)]-[poly(2-ethylhexyl acrylate)-(poly(methyl methacrylate)],[poly(methyl methacrylate)]-[poly(ethyl acrylate)-[poly(methylmethacrylate)], [poly(methyl methacrylate)]-[poly(n-butylacrylate)-[poly(methyl methacrylate)], and [poly(methylmethacrylate)]-[poly(2-ethylhexyl acrylate)-[poly(methyl methacrylate)].Of these, triblock copolymers made of [poly(methylmethacrylate)]-[poly(n-butyl acrylate)-[poly(methyl methacrylate)], and[poly(methyl methacrylate)]-[poly(2-ethylhexyl acrylate)-[poly(methylmethacrylate)] are particularly preferable since the molded product, theskin material, the painted film, and the like that are obtained from thethermoplastic polymer powder of the present invention are better inflexibility.

The ratio of each of the polymer blocks contained in the acrylic blockcopolymer (I) is not particularly limited. The ratio of the acrylicester polymer block(s) (A) is preferably from 20 to 95% by mass, morepreferably from 30 to 80% by mass of the acrylic block copolymer (I) tomake good the melt fluidity of the thermoplastic polymer powder of thepresent invention and make good the flexibility of the molded product,the skin material, the painted film, and the like that are obtainedtherefrom.

In order to make better the heat resistance of the molded product, theskin material, the painted film, and the like that are obtained from thethermoplastic polymer powder of the present invention, the ratio of themethacrylic ester polymer block(s) (B) is preferably from 5 to 80% bymass, in particular preferably from 20 to 70% by mass of the acrylicblock,copolymer (I) [in the case that the copolymer comprises no acrylicester polymer block (C)], the total ratio of the methacrylic esterpolymer block(s) (B) and the acrylic ester polymer block(s) (C) ispreferably from 5 to 80% by mass, in particular preferably from 20 to70% by mass of the copolymer (I) [in the case that the copolymer (I)comprises both of the methacrylic ester polymer block(s) (B) and theacrylic ester polymer block(s) (C)], or the ratio of the acrylic esterpolymer block(s) (C) is preferably from 5 to 80% by mass, in particularpreferably from 20 to 70% by mass of the copolymer (I) [in the case thatthe copolymer (I) comprises no methacrylic ester polymer block (B)].

The molecular weight of each of the polymer blocks constituting theacrylic block copolymer (I) may be any value that gives the dynamicviscosity properties prescribed in the (ii) and (iii) to thethermoplastic polymer powder of the present invention. In general, theweight average molecular weight of the acrylic ester polymer block(s)(A) is preferably from 1,000 to 150,000, in particular preferably from5,000 to 80,000, and the weight average molecular weights of themethacrylic ester polymer block(s) (B) and the acrylic ester polymerblock(s) (C) are preferably from 2,000 to 50,000, in particularpreferably from 5,000 to 25,000.

The molecular weight of the whole of the acrylic block copolymer (I) maybe any value that gives the dynamic viscosity properties prescribed inthe (ii) and (iii) to the thermoplastic polymer powder of the presentinvention. In general, the weight average molecular weight thereof ispreferably from 5,000 to 200,000, more preferably from 10,000 to100,000.

In the case that the acrylic block copolymer (I) is the above-mentionedtriblock copolymer made of [poly(methyl methacrylate)]-[poly(n-butylacrylate)-[poly(methyl methacrylate)] or [poly(methylmethacrylate)]-[poly(2-ethylhexyl acrylate)-[poly(methyl methacrylate)],the weight average molecular weight of the poly(methylmethacrylate)block corresponding to one of the methacrylic ester polymer blocks (B)is preferably from 2,000 to 25,000, in particular preferably from 5,000to 15,000 since the melt fluidity of the thermoplastic polymer powder ofthe present invention becomes good and further the flexibility of themolded product, the skin material, the painted film, and the like thatare obtained by use of the thermoplastic polymer powder becomes good.

In particular, in the-case that the weight average molecular weight ofthe poly(methyl methacrylate) block corresponding to one of themethacrylic ester polymer blocks (B) is from6,000 to 13,000 and themolecular weight of the whole of the acrylic block copolymer (I) is from30,000 to 70,000, the thermoplastic polymer powder of the invention isvery good in melt fluidity and has an excellent moldability even if nofluidity improver, plasticizer or the like is added thereto.

The acrylic block copolymer (I) constituting the thermoplastic polymerpowder of the invention can be produced according to any known methodfor producing an acrylic block copolymer. For example, a method ofliving-polymerizing monomers constituting the respective blocks isgenerally used. Examples of such a living-polymerizing method include amethod of subjecting the monomers to anionic polymerization in thepresence of a mineral acid salt, such as an alkali metal or alkalineearth metal salt, using an organic alkali metal compound as apolymerization initiator (see JP-B-7-25859); a method of subjecting themonomers to anionic polymerization in the presence of an organicaluminum compound, using an organic alkali metal compound as apolymerization initiator (see JP-A-11-335432); a method of polymerizingthe monomers, using an organic rare earth metal complex as apolymerization initiator (see JP-A-6-93060); and a method ofradical-polymerizing the monomers in the presence of a copper compound,using an a-halogenated ester compound as an initiator (see“Macromolecular Chemical Physics”, 2000, Vol. 201, pp. 1108-1114). Otherexamples thereof include a method of using a polyvalent radicalpolymerization initiator or polyvalent radical chain transfer agent topolymerize monomers constituting the respective blocks, therebyproducing a mixture containing the acrylic block copolymer (I)constituting the thermoplastic polymer powder of the invention.

Of these methods, the method of using an organic alkali metal compoundas a polymerization initiator to subject the monomers to anionicpolymerization in the presence of an organic aluminum compound ispreferably adopted since the method makes it possible to yield theacrylic block copolymer (I) with a high purity, causes the molecularweight and the composition ratio to be easily controlled and is furthereconomical.

The thermoplastic polymer powder of the present invention needs to havea complex dynamic viscosity η*(5) of 5.0×1 Pa.s or less, the viscosityη*(5) being measured under conditions of a temperature of 250° C. and anangular frequency of 5 rad/sec [the above-mentioned requirement (ii)].The complex dynamic viscosity η*(5) is preferably 1.0×10³ Pa.s or less,more preferably 5.0×10² Pa.s or less. If the complex dynamic viscosityη*(5) at a temperature of 250° C. and a frequency of 5 rad/sec is morethan 5.0×10³ Pa.s, the thermoplastic polymer powder is not melted on thesurface of a mold so that the powder becomes unsuitable for powder slushmolding, which is performed in the state that the shear rate is a verylow value of 1 sec⁻¹ or less and fashioning pressure is notsubstantially applied thereto.

Furthermore, the thermoplastic polymer powder of the invention needs tohave a Newtonian viscosity index n of 0.50 or less [the above-mentionedrequirement (iii)], the index n being represented by the followingequation (1):n=log η*(5)-log η*(50)   (1)wherein n represents the Newtonian viscosity index, η*(5) represents thecomplex dynamic viscosity (unit: Pa.s) measured under conditions of atemperature of 250° C. and an angular frequency of 5 rad/sec, and η*(50)represents the complex dynamic viscosity (unit: Pa.s) measured underconditions of a temperature of 250° C. and an angular frequency of 50rad/sec. The Newtonian viscosity index n is preferably 0.30 or less,more preferably 0.20 or less.

In the case that the Newtonian viscosity index n of the thermoplasticpolymer powder is more than 0.50, the frequency dependency of thecomplex dynamic viscosity is large even if the viscosity η*(5) measuredunder conditions of a temperature of 250° C. and an angular frequency of5 rad/sec is 5.0×10³ Pa.s or less. As a result, thermal fusion betweenthe melted thermoplastic polymer powder particles becomes incomplete inmolding methods, such as slush molding, wherein the shear rate is a verylow value of 1 sec⁻¹ or less when the powder is molded or the fashioningpressure is a small value of 1 kg/cm² or less when the powder is molded.Consequently, only a molded product poor in mechanical properties isobtained.

The complex dynamic viscosity η*(5) (unit: Pa.s) of the thermoplasticpolymer powder of the invention, which is measured m under conditions ofa temperature of 250° C. and an angular frequency of 5 rad/sec, and thecomplex dynamic viscosity η*(50) (unit: Pa.s) thereof, which is measuredunder conditions of a temperature of 250° C. and an angular frequency of50 rad/sec, are each a value when an ARES viscoelasticity measuringsystem manufactured by Rheometric Scientific Co. is used to measure thedynamic viscosity of the thermoplastic polymer powder itself under acondition of a temperature of 250° C. and an angular frequency of 5rad/sec or 50 rad/sec before the powder is turned into a molded product.Details thereof are as described in the paragraph of Examples, whichwill be described later.

About the thermoplastic polymer powder of the invention, the meltviscosity measured under conditions of a temperature of 250° C. and ashear rate of 0.2 sec⁻¹ is preferably 3000 Pa.s or less, more preferably2000 Pa.s or less, even more preferably 1500 Pa.s or less.

If the melt viscosity measured under conditions of a temperature of 250°C. and a shear rate of 0.2 sec⁻¹ is 3000 Pa.s or more, the thermoplasticpolymer powder is easily not melted on the surface of a mold so that thepowder easily becomes unsuitable for slush molding, which is performedin the state that the shear rate is a very low value of 1 sec⁻¹ or lessand fashioning pressure is not substantially applied thereto.

The average particle diameter of the thermoplastic polymer powder of theinvention is indispensably 1 mm or less, preferably 800 μm or less, morepreferably from 50 to 500 μm. If the average particle diameter of thethermoplastic polymer powder is more than 1 mm, the powder fluidity orthe weighability of the powder easily gets poor when the powder issubjected to slush molding, rotational molding, some other molding usingthe powder, powder coating, or the like. As a result, a molded product,a skin material, a painted film or the like that has a high quality isnot easily obtained. In the case that the thermoplastic polymer powderof the invention is used, in particular, in slush molding, it ispreferred that the average particle diameter of the thermoplasticpolymer powder is from 50 to 500 μm from the viewpoint of good workingconditions, the evenness of the thickness of the resultant moldedproduct, the prevention of the generation of pinholes, mechanicalstrength, and others.

The average particle diameter of the thermoplastic polymer powder in thepresent specification means average particle diameter measured with ascattering system particle size distribution measuring device (forexample, “LA-920” manufactured by HORIBA).

As long as the thermoplastic polymer powder of the invention satisfiesthe above-mentioned requirements (i) to (iv), the powder may be a powdermade only of the acrylic block copolymer (I) or a powder made of anacrylic block copolymer (I) composition wherein a different component(such as a different polymer or an additive) is incorporated into theacrylic block copolymer (I).

In the case that the thermoplastic polymer powder of the invention ismade of an acrylic block copolymer (I) composition which comprises theacrylic block copolymer (I) and a different polymer, the content bypercentage of the different polymer can be varied by the kind of thedifferent polymer and so on and generally the content is preferably 40%by mass or less of the acrylic block copolymer (I) composition since theadvantageous effects which the thermoplastic polymer powder of theinvention has are not taken away from. The content is more preferably20% by mass or less.

Examples of the different polymer, which the thermoplastic polymerpowder of the invention may comprise together with the acrylic blockcopolymer (I), include olefin resins such as polyethylene,polypropylene, polybutene-1, poly-4-methylpentene-1, and polynorbornene;ethylene-based ionomers; styrene-based resins such as polystyrene,styrene/maleic anhydride copolymer, high impact polystyrene, AS resin,ABS resin, AES resin, AAS resin, ACS resin, and MBS resin; acrylicresins such as polymethyl methacrylate; methyl methacrylate/styrenecopolymer; polyester resins such as polyethylene terephthalate andpolybutylene terephthalate; polyamides such as nylon 6, nylon 66, andpolyamide elastomer; polycarbonate, polyvinyl chloride, polyvinylidenechloride, polyvinyl alcohol, ethylene/vinyl alcohol copolymer,polyacetal, polyvinylidene fluoride, polyurethane, modifiedpolyphenyleneether, polyphenylenesulfide, silicone rubber modifiedresin; acrylic rubbers; silicone rubbers; styrene-based thermoplasticrubbers such as SEPS, SEBS and SIS; and rubbers such as IR, EPR andEPDM. The powder may comprise one or more out of these polymers. Ofthese polymers, acrylic resins are preferably used since they areexcellent in compatibility with the acrylic block copolymer (I), whichis a constituent of the thermoplastic polymer powder.

Examples of the additive, which may be contained in the thermoplasticpolymer powder of the invention if necessary, include a lubricant, afluidity improver, a plasticizer (softener), a thermal stabilizer, aweatherability improver, an antioxidant, a light stabilizer, anantistatic agent, a flame retardant, an adhesive agent, a tackifier, afoaming agent, a pigment, a dye, a filler, and a reinforcing agent. Morespecific examples thereof include mineral oil softeners, such asparaffin oil and naphthene oil, for improving the fluidity when thepowder is molded; inorganic fillers, such as calcium carbonate, talc,carbon black, titanium oxide, silica, clay, barium sulfate, andmagnesium carbonate, for attaining an improvement in heat resistance,weatherability or the like, an increase in weight, and other objects;and inorganic or organic fibers, such as glass fiber and carbon fiber,for reinforcement. In order to make the heat resistance and theweatherability better, it is practically preferred that thethermoplastic polymer powder of the invention comprises a thermalstabilizer, an antioxidant or the like among these additives.

Even if the acrylic block copolymer (I) alone does not satisfy the (ii)or (iii), the incorporation of a fluidity improver or plasticizer maymake it possible to yield a powder exhibiting good fluidity. Inparticular, the incorporation of a fluidity improver or plasticizerhaving an SP value close to the SP value of the monomers which arepolymer block constituent units which constitute the acrylic blockcopolymer (I) makes it possible to yield, in many cases, a powder whichsatisfies the requirements (ii) and (iii) and is excellent in meltfluidity while preventing bleed-out and fogging. Examples of thefluidity improver or plasticizer that is preferably used at this timeinclude phosphoric acid derivatives such as tricresyl phosphate (21.4);citric acid derivatives such as acetyl tri(n-butyl) citrate (20.1);sebacic acid derivatives such as di(2-ethylhexyl) sebacate (18.1);adipic acid derivatives such as diisononyl adipate (18.2); phthalic acidderivatives such as diisononyl phthalate (19.2); and polyester oligomersand poly(meth)acrylic ester oligomers [the values inside the parenthesesare SP values]. The use of acetyl tri(n-butyl) citrate out of these ismore preferred from the viewpoint of bleed-out resistance and safety.When the fluidity improver or plasticizer is incorporated, theincorporated amount thereof is preferably 300 parts or less by mass,more preferably 150 parts or less by mass for 100 parts by mass of theacrylic block copolymer (I).

In the case that the thermoplastic polymer powder is made only of theacrylic block copolymer (I) without containing any different polymer oradditive, the process for producing the thermoplastic polymer powder ofthe invention is, for example, a process of making the acrylic blockcopolymer (I) obtained by polymerization directly into a powder in anappropriate manner, and optionally classifying the powder by use of asieve or the like.

In the case that the thermoplastic polymer powder of the presentinvention is made of an acrylic block copolymer (I) compositioncomprising the acrylic block copolymer (I) together with a differentpolymer and/or an additive, the mixing may be the respective componentsconstituting the composition collectively or separately, and thekneading may be the resultant mixture by use of a conventional kneadingmachine such as a single screw extruder, a twin screw extruder, aBanbury mixer, a Brabender, an open roll or kneader, so as to prepare,for example, a pellet-form acrylic block copolymer (I), next making theresultant into a powder in an appropriate manner, and optionallyclassifying the powder with a sieve or the like.

At the time of the kneading for obtaining the acrylic block copolymer(I) composition, this composition can be made homogenous by dry-blendingrespective components to be kneaded by use of a mixer such as a Henschelmixer or a tumbler before the kneading, and then supplying the resultantinto a kneading machine without supplying the components directly intothe kneading machine. The temperature for kneading the acrylic blockcopolymer (I) composition can be appropriately adjusted in accordancewith the melting temperature of the used acrylic block copolymer (I) andother factors. Usually, the components may be kneaded within atemperature ranging from 110 to 300° C.

In the above description, the method for making the acrylic blockcopolymer (I) itself or the acrylic block copolymer (I) composition intoa powder is not particularly limited, and may be any method that is usedat the time of making a thermoplastic polymer composition into a powder.For example, the following may be used; a method of using an impactpulverizing machine such as a turbo mill, a pin mill, a hummer mill, ora rotor speed mill to pulverize the acrylic block copolymer (I) itselfor a lump or pellets of the acrylic block copolymer (I) composition atambient temperature or under frozen conditions; a method of heating andmelting the acrylic block copolymer (I) itself or the acrylic blockcopolymer (I) composition, spraying the resultant with a spray device, adisk atomizer or the like, and then cooling the sprayed material; amethod of extruding the acrylic block copolymer (I) itself or theacrylic block copolymer (I) composition through a micro-dice into waterwith an extruder, and then hot-cutting the resultant in the water; orthe like.

Of the above-mentioned methods, the method of using an impactpulverizing machine to pulverize the copolymer or the composition atambient temperature or under frozen conditions is preferably adoptedsince facilities therefor are inexpensive and the production is easy.

The process of extruding the copolymer or composition through amicro-dice into water and then hot-cutting the resultant in the water isadvantageous, in particular, in the case that the thermoplastic polymerpowder is made of the acrylic block copolymer (I) composition. This isbecause the acrylic block copolymer (I) composition can be prepared andsimultaneously made into a powder by use of an extruder. In the case ofthe method of extruding the copolymer or composition through amicro-dice into water and then hot-cutting the resultant in the water,the extruded product is oriented to a high degree by shearing applied atthe time of the extrusion from the micro-dice; accordingly, the powderobtained by cutting it is less agglutinated so as to have excellentpowder fluidity. From this point, the method is preferred.

In the case that a powder having an average particle diameter of 1 mm orless is directly obtained by the above-mentioned pulverizing method, thepowder may be collected, as it is, as the thermoplastic polymer powderof the invention. In the case that the average particle diameter of thepowder obtained by the above-mentioned pulverizing method is more than 1mm or in the case that the average particle diameter is 1 mm or less andthe diameter is desired to be made smaller, it is advisable to classifythe powder obtained by the above-mentioned pulverizing method with asieve, a duct collector or the like and then collect powder having anaverage particle size of 1 mm or less, or smaller powder.

The thermoplastic polymer powder of the invention can be usedeffectively for molding technique or coating technique using a powderythermoplastic polymer or thermoplastic polymer powder composition. Thethermoplastic polymer powder can be used in powder moldings such asslush molding, rotational molding, compression molding, powder flamespraying, extrusion molding and calendaring, and various coatingtechniques using powder (such as fluidized bed coating process,electrostatic coating, thermal spraying, and spray painting), and can bemade into various molded products such as a sheet-form product, afilm-form product, a hollow product and a laminate, a skin material, apainted film, a coating product, and so on. The thermoplastic polymerpowder of the invention is particularly suitable for being used in slushmolding and rotational molding.

For example, a skin material having an uneven pattern in a skin grainform, a stitch form or some other form, or having a complicated shapecan be obtained by performing powder molding, such as slush molding,using the thermoplastic polymer powder of the invention. The moldedproduct, the skin material, and the painted film, and the like that areobtained by use of the thermoplastic polymer powder of the invention isexcellent in weatherability, and also excellent in flexibility,mechanical strength, low-temperature properties, rubber elasticity andothers. Furthermore, the weatherability of the acrylic block copolymer(I), which is a constituent, is good, and thus the molded body and thelike obtained therefrom are also excellent in weatherability.Additionally, the thermoplastic polymer powder does not contain anyhalogen such as chlorine or any plasticizer; therefore, environmentalpollution is not caused when the powder is burned, so as not to cause ananxiety about carcinogenicity. Thus, the safety thereof and others arealso excellent.

If necessary, the molded product, the skin material, the painted filmand the like that are obtained by use of the thermoplastic polymerpowder of the invention may be subjected to surface coating with, forexample, polyurethane.

An article having a molded product, a skin material or a painted filmobtained by use of the thermoplastic polymer powder of the inventionmakes good use of various properties such as superior flexibility,rubber elasticity, low-temperature properties, mechanical strength,weatherability, safety, and no inducement of environmental pollution,thereby making it possible that the article is effectively applied tovarious purposes, such as automobile interior members such as aninstrument panel, a door trim, a console box, an arm rest, a head rest,a seat, a pillar, a steering wheel, and a ceiling; skin materials for asofa and various chairs; sporting goods; leisure goods; stationery;lining for houses; mannequins; and others. In particular, thethermoplastic polymer powder having such a flexibility that the JIS-Ahardness ranges from 40 to 95 can be used in particular suitably for toymembers. The thermoplastic polymer powder having a JIS-A hardness of 95or more can be effectively used for articles for which theweatherability and the transparency of the thermoplastic polymer powderare utilized, for example, outdoor parts such as a street light glove,eaves and a top cover; tanks such as a living fish tank, and anindustrial tank; and a lighting cover.

EXAMPLES

The present invention will be specifically described by way of thefollowing examples and so on. However, the present invention is notlimited to the examples.

In each of the following examples, the weight average molecular weightsof the whole of the block copolymer and the polymethyl methacrylate(PMMA) block, the constituting percentage of each of polymer blocks, theaverage particle diameter, the melt viscosity, the dynamic viscosity(complex dynamic viscosity), and the slush moldability of athermoplastic polymer powder, the flexibility (hardness), the tensilestrength and the elongation at break of the molded product obtainedtherefrom were measured or evaluated by the following methods:

(1) Weight Average Molecular Weights of the Whole of Block Copolymer,and PMMA Block:

In each of referential examples described below, the weight averagemolecular weights of the whole of the block copolymer and the PMMA blockwere obtained as molecular weights in terms of polystyrene by gelpermeation chromatography (hereinafter referred to as GPC).

(2) Constituting Percentage of Each of Polymer Blocks in BlockCopolymer:

In each of referential examples described below, the constitutingpercentage of each of polymer blocks in the block copolymer was obtainedby ¹H-NMR measurement.

(3) Average Particle Diameter of Thermoplastic Polymer Powder:

The average particle diameter of the thermoplastic polymer powderobtained in each of the following examples and comparative examples wasmeasured by use of a scattering system particle size measuring device(“LA-920” manufactured by HORIBA).

(4) Melt Viscosity of Thermoplastic Polymer Particles:

The thermoplastic polymer powder obtained in each of the followingexamples and comparative examples and a Brookfield viscometer (modelnumber: RVDV-II+) manufactured by Brookfield Co. were used to measurethe melt viscosity under conditions of a temperature of 250° C. and ashear rate of 0.2 sec⁻¹.

(5) Dynamic Viscoelasticity and Complex Dynamic Viscosity ofThermoplastic Polymer Powder:

The thermoplastic polymer powder obtained in each of the followingexamples and comparative examples and an ARES viscoelasticity measuringsystem manufactured by Rheometric Scientific Co. were used to measurethe dynamic viscoelasticities at a temperature of 250° C. and angularfrequencies of 5 rad/sec and 50 rad/sec. From the resultant dynamicviscoelasticity values, the complex dynamic viscosities η*(5)and η*(50)were calculated. The measurement of the dynamic viscoelasticities wasmade in a parallel flat plate mode (dynamic frequency sweep; the use ofplates of 25 mm in diameter). The applied strain was 0.5%.

The Newtonian viscosity index n was calculated on the basis of theabove-mentioned equation (1), using the values of the complex dynamicviscosities η*(5) and η*(50) calculated above.

(6) Slush Moldability:

The external appearance and the surface state of the sheet-form moldedproduct of 1 mm thickness obtained by slush molding in each of thefollowing examples and comparative examples were evaluated by visualcheck, and then the slush moldability thereof was evaluated inaccordance with the following evaluation criterion:

[Evaluation Criterion of the Slush Moldability]

⊚: The obtained sheet-form molded product exhibited a very smoothsurface state.

∘: The obtained sheet-form molded product exhibited a good surface stateand had no pinholes.

X: Irregularities in the surface were conspicuous and a large number ofpinholes were observed.

(7) Flexibility (Hardness) of Molded Product:

About the sheet-form molded product of 1 mm thickness obtained by slushmolding in each of the following examples and comparative examples, theflexibility (hardness) was measured in accordance with JIS K 6253.Specifically, a type A hardness meter (KOBUNSHI KEIKI CO., LTD.) wasused to make a durometer hardness test, thereby measuring the hardness.

(8) Tensile Strength and Elongation at Break of Molded Product:

From the sheet-form molded product of 1 mm thickness obtained by slushmolding in each of the following examples and comparative examples, atest piece was punched out with a JIS No. 3 punching blade. The tensilestrength and the elongation at break were measured in accordance withJIS K 6251.

Referential Example 1 Synthesis of Acrylic Block Copolymer

(1) A 1-liter three-necked flask was equipped with a three-way stopcock,and the inside thereof was degassed and purged with nitrogen.Thereafter, into the flask was charged with 278 g of toluene, 13.9 g of1,2-dimethoxyethane, and 12.2 g of a toluene solution containing 8.18mmol of isobutylbis(2,6-di-t-butyl-4-methylphenoxy)aluminum.Furthermore, 1.68 mmol of sec-butyllithium was added thereto. Theretowas added17.0 g of methyl methacrylate, and then the components werecaused to react at room temperature for 1 hour. One gram was collectedas a sample lout of this reaction solution. Subsequently, the insidetemperature of the polymer solution was cooled to −30° C., and then 79.0g of n-butyl acrylate was dropwise added thereto over 5 hours. One gramwas collected as a sample 2 out of this reaction solution. Subsequently,thereto was added 17.0 g of methyl methacrylate, and the temperature ofthe reaction solution was raised to room temperature. The componentstherein were caused to react while the solution was stirred for 10hours. This reaction solution was poured into a large amount ofmethanol, and the thus-obtained precipitate was separated and collectedas an acrylic block copolymer [referred to as the “triblock copolymer(a)” hereinafter].

(2) The sample 1, the sample 2 and the triblock copolymer (a) obtainedin the paragraph (1) were each subjected to GPC measurement and ¹H-NMRmeasurement, and on the basis of the obtained results, the Mw (weightaverage molecular weight) of the whole, the. Mw/Mn (molecular weightdistribution) thereof, the ratio by mass between the polymethylmethacrylate (PMMA) blocks and the poly(n-butyl acrylate) (PnBA) blocktherein, and so on were obtained. As a result, the triblock copolymer(a) was a triblock copolymer made of block PMMA-block PnBA-block PMMA.The Mw of the PMMA blocks at both ends of this triblock copolymer (a)was 10,400, and the Mw/Mn thereof was 1.07. The Mw of the whole of thetriblock copolymer (a) was 77,000 and the Mw/Mn thereof was 1.10. Thepercentage of each of the polymer blocks was as follows: PMMA (15% bymass)-PnBA (70% by mass)-PMMA (15% by mass).

Referential Example 2 Synthesis of Acrylic Block Copolymer

A triblock copolymer made of block PMMA-block PnBA-block PMMA[hereinafter referred to as the “triblock copolymer (b)”] was producedby adopting the same method as in Referential Example 1 except that theamounts of the supplied monomers were changed.

The Mw of the PMMA blocks at both ends of this triblock copolymer. (b)was 10,600, and the Mw/Mn thereof was 1.07. The Mw of the whole of thetriblock copolymer (b) was 60,800 and the Mw/Mn thereof was 1.04. Thepercentage of each of the polymer blocks in this triblock copolymer (b)was as follows: PMMA (20% by mass)-PnBA (60% by mass)-PMMA (20% bymass).

Referential Example 3 Synthesis of Acrylic Block Copolymer

A triblock copolymer made of block PMMA-block PnBA-block PMMA[hereinafter referred to as the “triblock copolymer (c)”] was producedby adopting the same method as in Referential Example 1 except that theamounts of the supplied monomers were changed.

The Mw of the PMMA blocks at both ends of this triblock copolymer (c)was 7,100, and the Mw/Mn thereof was 1.13. The Mw of the whole of thetriblock copolymer (c) was 82,000 and the Mw/Mn thereof was 1.13. Thepercentage of each of the polymer blocks in this triblock copolymer (c)was as follows: PMMA (12.5% by mass)-PnBA (75% by mass)-PMMA (12.5% bymass).

Referential Example 4 Synthesis of Acrylic Block Copolymer

A triblock copolymer made of block PMMA-block PnBA-block PMMA[hereinafter referred to as the “triblock copolymer (d)”] was producedby adopting the same method as in Referential Example 1 except that theamounts of the supplied monomers were changed.

The Mw of the PMMA blocks at both ends of this triblock copolymer (d)was 11,300, and the Mw/Mn thereof was 1.07. The Mw of the whole of thetriblock copolymer (d) was 116,000 and the Mw/Mn thereof was 1.06. Thepercentage of each of the polymer blocks in this triblock copolymer (d)was as follows: PMMA (12.5% by mass)-PnBA (75% by mass)-PMMA (12.5% bymass).

Referential Example 5 Synthesis of Acrylic Block Copolymer

A triblock copolymer made of block PMMA-block PnBA-block PMMA[hereinafter referred to as the “triblock copolymer (e)”] was producedby adopting the same method as in Referential Example 1 except that theamounts of the supplied monomers were changed.

The Mw of the PMMA blocks at both ends of this triblock copolymer (e)was 8,300, and the Mw/Mn thereof was 1.08. The Mw of the whole of thetriblock copolymer (e) was 54,000 and the Mw/Mn thereof was 1.07. Thepercentage of each of the polymer blocks in this triblock copolymer (e)was as follows: PMMA (17.5% by mass)-PnBA (65% by mass)-PMMA (17.5% bymass).

Referential Example 6 Synthesis of Acrylic Block Copolymer

A triblock copolymer made of block PMMA-block PnBA-block PMMA[hereinafter referred to as the “triblock copolymer (f)”] was producedby adopting the same method as in Referential Example 1 except that theamounts of the supplied monomers were changed.

The Mw of the PMMA blocks at both ends of this triblock copolymer (f)was 10,900, and the Mw/Mn thereof was 1.12. The Mw of the whole of thetriblock copolymer (f) was 37,000 and the Mw/Mn thereof was 1.08. Thepercentage of each of the polymer blocks in this triblock copolymer (f)was as follows: PMMA (30% by mass)-PnBA (40% by mass)-PMMA (30% bymass).

Referential Example 7 Synthesis of Acrylic Block Copolymer

A triblock copolymer made of block PMMA-block PnBA-block PMMA[hereinafter referred to as the “triblock copolymer (g)”] was producedby adopting the same method as in Referential Example 1 except that theamounts of the supplied monomers were changed.

The Mw of the PMMA blocks at both ends of this triblock copolymer (g)was 7,600, and the Mw/Mn thereof was 1.14. The Mw of the whole of thetriblock copolymer (g) was 49,000 and the Mw/Mn thereof was 1.10. Thepercentage of each of the polymer blocks in this triblock copolymer (g)was as follows: PMMA (15% by mass)-PnBA (70% by mass)-PMMA (15% bymass).

The details of the acrylic block copolymers obtained in theabove-mentioned Referential Examples 1 to 7 are as shown in thefollowing Table 1.

Table 1

Example 1 Production and Slush Molding of Thermoplastic Polymer Powder

(1) An impact pulverizer (“Rotor Speed Mill P-14”, manufactured byFritsche Co.) was used to pulverize the triblock copolymer (a) obtainedin Referential Example 1 at a temperature of −100° C., and then thepulverized product was classified with a 32-mesh sieve (sieve opening:0.495 mm). The powder which passed through the sieve was collected as athermoplastic polymer powder.

The average particle diameter and the melt viscosity of the resultantthermoplastic polymer powder were measured by the above-mentionedmethods. The results are as shown in Table 2 described below.

The complex dynamic viscosity η*(5) and the complex dynamic viscosityη*(50) of the resultant thermoplastic polymer powder were calculated bythe above-mentioned method, and further the Newtonian viscosity index nthereof was obtained from these values on the basis of theabove-mentioned equation (1). The results are as shown in Table 2.

(2) The thermoplastic polymer powder obtained in the paragraph (1) wasuniformly sprinkled on a mold made of a nickel electroformed plate(length=width=thickness=150 mm×150 mm×1 mm) having a surface temperatureof 250° C. The powder was kept at the same temperature for 30 seconds inthe state that the powder was allowed to stand still. In this way, thethermoplastic polymer powder was melted and stuck thereto, andsubsequently the electroformed plate was rotated, thereby dischargingthe powder that was not melted or stuck. The electroformed plate ontowhich the thermoplastic polymer powder was melted and stuck was kept ina heating furnace of 250° C. temperature for 3 minutes, so as to meltthe powder. Next, the resultant was taken out from the heating furnaceand cooled to 40° C. with water, and then the polymer was removed fromthe mold, so as to produce a sheet-form molded product (slush moldedproduct) of 1 mm thickness. The slush moldability at this time wasevaluated by the above-mentioned method. The result is as shown in Table2.

(3) A given test piece was obtained from the sheet-form molded productobtained in the paragraph (2), and the flexibility (hardness), thetensile strength and the elongation at break thereof were measured bythe above-mentioned methods. The results are as shown in Table 2.

Example 2 Production and Slush Molding of Thermoplastic Polymer Powder

(1) An extruder was used to extrude the triblock copolymer (a) obtainedin Referential Example 1 through a micro-dice having pores of 500 μmdiameter into water. Underwater palletizing systems (manufactured byGala Co.) were used to hot-cut the extruded copolymer in water (at atemperature of 80° C.), thereby producing a thermoplastic polymerpowder.

The average particle diameter and the melt viscosity of the resultantthermoplastic polymer powder were measured by the above-mentionedmethods. The results are as shown in Table 2.

The complex dynamic viscosity η*(5) and the complex dynamic viscosityη*(50) of the resultant thermoplastic polymer powder were calculated bythe above-mentioned method, and further the Newtonian viscosity index nthereof was obtained from these values on the basis of theabove-mentioned equation (1). The results are as shown in Table 2.

(2) The thermoplastic polymer powder obtained in the paragraph (1) wasused to perform slush molding in the same way as in the paragraph (2) ofExample 1, thereby producing a sheet-form molded product of 1 mm inthickness. The slush moldability at this time was evaluated by theabove-mentioned method. The result is as shown in Table 2.

(3) A given-test piece was obtained from the sheet-form molded productobtained in the paragraph (2), and the flexibility (hardness), thetensile strength and the elongation at break thereof were measured bythe above-mentioned methods. The results are as shown in Table 2.

Example 3 Production and Slush Molding of Thermoplastic Polymer Powder

(1) A thermoplastic polymer powder was produced in the same way as inthe paragraph (1) of Example 1 except that the triblock copolymer (b)obtained in Referential Example 2 was used.

The average particle diameter and the melt viscosity of the resultantthermoplastic polymer powder were measured by the above-mentionedmethods. The results are as shown in Table 2.

The complex dynamic viscosity η*(5) and the complex dynamic viscosityη*(50) of the resultant thermoplastic polymer powder were calculated bythe above-mentioned method, and further the Newtonian viscosity index nthereof was obtained from these values on the basis of theabove-mentioned equation (1). The results are as shown in Table 2.

(2) The thermoplastic polymer powder obtained in the paragraph (1) wasused to perform slush molding in the same way as in the paragraph (2) ofExample 1, thereby producing a sheet-form molded product of 1 mm inthickness. The slush moldability at this time was evaluated by theabove-mentioned method. The result is as shown in Table 2.

(3) A given test piece was obtained from the sheet-form molded productobtained in the paragraph (2), and the flexibility (hardness), thetensile strength and the elongation at break thereof were measured bythe above-mentioned methods. The results are as shown in Table 2.

Example 4 Production and Slush Molding of Thermoplastic Polymer Powder

(1) Ninety parts by mass of the triblock copolymer (c) obtained inReferential Example 3 were mixed with 10 parts by mass of a methacrylicresin [Mw=37,000, Mw/Mn=1.6, and copolymerization ratio of methylmethacrylate to methyl acrylate=86 : 14 (ratio by mass)] as anothercomponent, and then the mixture was melted and kneaded in a Laboplastmill at 200° C., so as to prepare a triblock copolymer (c) composition.

(2) The triblock copolymer (c) composition obtained in the paragraph (1)was used to produce a thermoplastic polymer powder in the same way as inthe paragraph (1) of Example 1.

The average particle diameter and the melt viscosity of the resultantthermoplastic polymer powder were measured by the above-mentionedmethods. The results are as shown in Table 2.

The complex dynamic viscosity η*(5) and the complex dynamic viscosityη*(50) of the resultant thermoplastic polymer powder were calculated bythe above-mentioned method, and further the Newtonian viscosity index nthereof was obtained from these values on the basis of theabove-mentioned equation (1). The results are as shown in Table 2.

(3) The thermoplastic polymer powder obtained in the paragraph (2) wasused to perform slush molding in the same way as in the paragraph (2) ofExample 1, thereby producing a sheet-form molded product of 1 mm inthickness. The slush moldability at this time was evaluated by theabove-mentioned method. The result is as shown in Table 2.

(4) A given test piece was obtained from the sheet-form molded productobtained in the paragraph (3), and the flexibility (hardness), thetensile strength and the elongation at break thereof were measured bythe above-mentioned methods. The results are as shown in Table 2.

Example 5 Production and Slush Molding of Thermoplastic Polymer Powder

(1) A thermoplastic polymer powder was produced in the same way as inthe paragraph (1) of Example 3 except that the triblock copolymer (e)obtained in Referential Example 5 was used.

The average particle diameter and the melt viscosity of the resultantthermoplastic polymer powder were measured by the above-mentionedmethods. The results are as shown in Table 2.

The complex dynamic viscosity η*(5) and the complex dynamic viscosityη*(50) of the resultant thermoplastic polymer powder were calculated bythe above-mentioned method, and further the Newtonian viscosity index nthereof was obtained from these values on the basis of theabove-mentioned equation (1). The results are as shown in Table 2.

(2) The thermoplastic polymer powder obtained in the paragraph (1) wasused to perform slush molding in the same way as in the paragraph (2) ofExample 1, thereby producing a sheet-form molded product (slush moldedproduct) of 1 mm in thickness. The slush moldability at this time wasevaluated by the above-mentioned method. The result is as shown in Table2.

(3) A given test piece was obtained from the sheet-form molded productobtained in the paragraph (2), and the flexibility (hardness), thetensile strength and the elongation at break thereof were measured bythe above-mentioned methods. The results are as shown in Table 2.

Example 6 Production and Slush Molding of Thermoplastic Polymer Powder

(1) A thermoplastic polymer powder was produced in the same way as inthe paragraph (1) of Example 3 except that the triblock copolymer (f)obtained in Referential Example 6 was used.

The average particle diameter and the melt viscosity of the resultantthermoplastic polymer powder were measured by the above-mentionedmethods. The results are as shown in Table 3.

The complex dynamic viscosity η*(5) and the complex dynamic viscosityη*(50) of the resultant thermoplastic polymer powder were calculated bythe above-mentioned method, and further the Newtonian viscosity index nthereof was obtained from these values on the basis of theabove-mentioned equation (1). The results are as shown in Table 3.

(2) The thermoplastic polymer powder obtained in the paragraph (1) wasused to perform slush molding in the same way as in the paragraph (2) ofExample 1, thereby producing a sheet-form molded product of 1 mm inthickness. The slush moldability at this time was evaluated by theabove-mentioned method. The result is as shown in Table 3.

(3) A given test piece was obtained from the sheet-form molded productobtained in the paragraph (2), and the flexibility (hardness), thetensile strength and the elongation at break thereof were measured bythe above-mentioned methods. The results are as shown in Table 3.

Example 7 Production and Slush Molding of Thermoplastic Polymer Powder

(1) A thermoplastic polymer powder was produced in the same way as inthe paragraph (1) of Example 3 except that the triblock copolymer (g)obtained in Referential Example 7 was used.

The average particle diameter and the melt viscosity of the resultantthermoplastic polymer powder were measured by the above-mentionedmethods. The results are as shown in Table 3.

The complex dynamic viscosity η*(5) and the complex dynamic viscosityη*(50) of the resultant thermoplastic polymer powder were calculated bythe above-mentioned method, and further the Newtonian viscosity index nthereof was obtained from these values on the basis of theabove-mentioned equation (1). The results are as shown in Table 3.

(2) The thermoplastic polymer powder obtained in the paragraph (1) wasused to perform slush molding in the same way as in the paragraph (2) ofExample 1, thereby producing a sheet-form molded product of 1 mm inthickness. The slush moldability at this time was evaluated by theabove-mentioned method. The result is as shown in Table 3.

(3) A given test piece was obtained from the sheet-form molded productobtained in the paragraph (2), and the flexibility (hardness), thetensile strength and the elongation at break thereof were measured bythe above-mentioned methods. The results are as shown in Table 3.

Example 8 Production and Slush Molding of Thermoplastic Polymer Powder

(1) Seventy parts by mass of the triblock copolymer (d) obtained inReferential Example 4 were mixed with 30 parts by mass of acetyltri(n-butyl) citrate (manufactured by Sanken Kakoh K. K.) as aplasticizer, and then the mixture was melted and kneaded in a Laboplastmill at 200° C., so as to prepare a triblock copolymer (d) composition.(2) The triblock copolymer (d) composition obtained in the paragraph (1)was used to produce a thermoplastic polymer powder in the same way as inthe paragraph (1) of Example 1. The average particle diameter and themelt viscosity of the resultant thermoplastic polymer powder weremeasured by the above-mentioned methods. The results are as shown inTable 3.

The complex dynamic viscosity η*(5) and the complex dynamic viscosityη*(50) of the resultant thermoplastic polymer powder were calculated bythe above-mentioned method, and further the Newtonian viscosity index nthereof was obtained from these values on the basis of theabove-mentioned equation (1). The results are as shown in Table 3.

(3) The thermoplastic polymer powder obtained in the paragraph (2) wasused to perform slush molding in the same way as in the paragraph (2) ofExample 1, thereby producing a sheet-form molded product of 1 mm inthickness. The slush moldability at this time was evaluated by theabove-mentioned method. The result is as shown in Table 3.

(4) A given test piece was obtained from the sheet-form molded productobtained in the paragraph (3), and the flexibility (hardness), thetensile strength and the elongation at break thereof were measured bythe above-mentioned methods. The results are as shown in Table 3.

Comparative Example 1 Production and Slush Molding of ThermoplasticPolymer Powder

(1) A thermoplastic polymer powder was produced in the same way as inthe paragraph (1) of Example 1 except that the triblock copolymer (d)obtained in Referential Example 4 was used.

The average particle diameter of the resultant thermoplastic polymerpowder was measured by the above-mentioned method. The result is asshown in Table 3. The melt viscosity of the resultant thermoplasticpolymer powder was also measured by the above-mentioned method. As aresult, the viscosity exceeded the measurement upper limit of aBrookfield viscometer. It was impossible to measure the viscosity.

The complex dynamic viscosity η*(5) and the complex dynamic viscosityη*(50) of the resultant thermoplastic polymer powder were calculated bythe above-mentioned method, and further the Newtonian viscosity index nthereof was obtained from these values on the basis of theabove-mentioned equation (1). The results are as shown in Table 3.

(2) The thermoplastic polymer powder obtained in the paragraph (1) wasused to perform slush molding in the same way as in the paragraph (2) ofExample 1. As a result, a molded product having a remarkably unevensurface wherein a large number of pinholes were generated was yielded.Thus, a normal sheet-form molded product was not obtained. Consequently,it was impossible to measure the flexibility (hardness), the tensilestrength and the elongation at break.

Comparative Example 2 Production and Slush Molding of ThermoplasticPolymer Powder

(1) A thermoplastic polymer powder was produced in the same way as inthe paragraph (1) of Example 1 except that a styrene-based copolymer(“SEPTON 2002”, manufactured by KURARAY CO., LTD.) was used instead ofthe triblock copolymer (a) obtained in Referential Example 1.

The average particle diameter of the resultant thermoplastic polymerpowder was measured by the above-mentioned method. The result is asshown in Table 3. The melt viscosity of the resultant thermoplasticpolymer powder was also measured by the above-mentioned method. As aresult, the viscosity exceeded the measurement upper limit of aBrookfield viscometer. It was impossible to measure the viscosity.

The complex dynamic viscosity η*(5) and the complex dynamic viscosityη*(50) of the resultant thermoplastic polymer powder were calculated bythe above-mentioned method, and further the Newtonian viscosity index nthereof was obtained from these values on the basis of theabove-mentioned equation (1). The results are as shown in Table 3.

(2) The thermoplastic polymer powder obtained in the paragraph (1) wasused to perform slush molding in the same way as in the paragraph (2) ofExample 1. As a result, a molded product having a remarkably unevensurface wherein a large number of pinholes were generated was yielded.Thus, a normal sheet-form molded product was not obtained. Consequently,it was impossible to measure the flexibility (hardness), the tensilestrength and the elongation at break.

Table 2 & Table 3

As can be seen from Tables 2 and 3, the thermoplastic polymer powders ofExamples 1 to 8 satisfy the above-mentioned requirements (i) to (iii)and further have a small average particle diameter of 1 mm or less so asto satisfy the requirement (iv), thereby making it possible to yieldmolded products which are excellent in slush moldability, are good insurface state and have no pinholes smoothly by slush molding. Moreover,the molded products by slush molding are excellent in mechanicalproperties.

Furthermore, it can be understood from the results in Tables 2 and 3that as long as the thermoplastic polymer powders of the invention areeach a thermoplastic polymer powder which is made mainly of an acrylicblock copolymer (I) satisfying the requirement (i) and which is furthera thermoplastic polymer powder satisfying the requirements prescribed inthe (ii) to (iv), the thermoplastic polymer powders are excellent inslush moldability even if the thermoplastic polymer powders are eachmade of the acrylic block copolymer (I) alone (Examples 1 to 3, andExamples 5 to 7) or are each made of a composition comprising theacrylic block copolymer (I) together with different components (Examples4 and 8).

The powder of Comparative Example 1, which is made of the acrylic blockcopolymer (I) obtained in Referential Example 4 (triblock copolymer (d)]alone, has a Newtonian viscosity index of more than 0.50, the indexbeing represented by the above-mentioned equation (1), so as not tosatisfy the above-mentioned requirement (iii). Thus, the powder is poorin melt fluidity so as to exhibit a poor slush moldability. Accordingly,in the molded product obtained by slush molding, the surface thereof isremarkably uneven and further a large number of pinholes are generated.

On the other hand, the thermoplastic polymer powder of Example 8 is apowder produced by use of a composition wherein acetyl tri(n-butyl)citrate (fluidity improver or plasticizer) is added to the triblockcopolymer (d), which does not satisfy the requirement (iii), andsatisfies not only the requirements (i) and (iv) but also therequirements (ii) and (iii), thereby exhibiting a high fluidity and anexcellent slush moldability in the same manner as the thermoplasticpolymer powders of Examples 1 to 7.

The powder of Comparative Example 2 has a Newtonian viscosity index ofmore than 0.50, the index being represented by the above-mentionedequation (1), in the same manner as Comparative Example 1, so as not tosatisfy the above-mentioned requirement (iii). Thus, the powder is poorin melt fluidity so as to exhibit a poor slush moldability. Accordingly,in the molded product obtained by slush molding, the surface thereof isremarkably uneven and further a large number of pinholes are generated.

INDUSTRIAL APPLICABILITY

The thermoplastic polymer powder of the present invention is excellentin moldability (in particular, melt fluidity) and can be usedeffectively in molding techniques using powder resin, such as slushmolding, rotational molding, compression molding, extrusion molding, andcalendaring, and further can be satisfactorily used in various powdercoating techniques. In particular, in the case that the powder is usedin slush molding, it is possible to produce smoothly a molded producthaving unevenness (an uneven pattern) in a skin grain form or in astitch form or having a complicated shape.

The molded product, the skin material, the painted film, and the likethat are obtained by use of the thermoplastic polymer powder of theinvention are excellent in weatherability, flexibility, low-temperatureproperties, rubber elasticity, texture, external appearance, adhesion topolar resins, and others.

The thermoplastic polymer powder of the invention does not contain anyplasticizer that is suspected to be environmental disrupter or havecarcinogenicity, and the polymer components and so on that constitutethe thermoplastic polymer powder do not contain any halogen; therefore,the powder does not cause anxiety of the generation of dioxin by theincineration thereof or carcinogenicity, so as to exhibit an excellentsafety.

The thermoplastic polymer powder of the invention makes good use of theabove-mentioned excellent properties, thereby making it possible thatthe powder is effectively used for wide purposes, such as automobileinterior members such as an instrument panel, a door trim, a consolebox, an armrest, a headrest, a seat, a pillar, a steering wheel, and aceiling; skin materials for a sofa and various chairs; sporting goods;leisure goods; stationery; lining for houses; mannequins; toy members;outdoor parts such as a street light glove, eaves and a top cover; tankssuch as a living fish tank, and an industrial tank; and a lighteningcover. TABLE 1 Triblock copolymer Whole of triblock Percentage (% byReferential PMMA block copolymer mass) Example Symbol Structure Mw Mw/MnMw Mw/Mn PMMA/PnBA/PMMA 1 (a) PMMA-PnBA-PMMA¹⁾ 10,400 1.07 77,000 1.1015/70/15 2 (b) PMMA-PnBA-PMMA¹⁾ 10,600 1.07 60,800 1.04 20/60/20 3 (c)PMMA-PnBA-PMMA¹⁾ 7,100 1.13 82,000 1.13 12.5/75/12.5 4 (d)PMMA-PnBA-PMMA¹⁾ 11,300 1.07 116,000 1.06 12.5/75/12.5 5 (e)PNMA-PnBA-PMMA¹⁾ 8,300 1.08 54,000 1.07 17.5/65/17.5 6 (f)PMMA-PnBA-PMMA¹⁾ 10,900 1.12 37,000 1.08 30/40/30 7 (g) PMMA-PnBA-PMMA¹⁾7,600 1.14 49,000 1.10 15/70/15¹⁾[Polymethyl methacrylate]-[poly(n-butyl acrylate)]-[polymethylmethacrylate] triblock copolymer

TABLE 2 Example 1 Example 2 Example 3 Example 4 Example 5 [Thermoplasticpolymer particles] Formulation (parts by mass) Triblock copolymer (a)100 (a) 100 (b) 100 (c) 90 (e)100 Methacrylic resin 10 Styrene-basedblock copolymer Acetyl tri(n-butyl) citrate Complex dynamic viscosityη*(5) (Pa.s) 40.6 40.6 152 33.4 <20 η*(50) (Pa.s) 40.5 40.5 148 29.4 <20Newtonian viscosity index n 0.001 0.001 0.01 0.05 <0.1 Average particlediameter (μm) 430 550 450 390 250 Melt viscosity (Pa.s) 40 40 140 30 6Slush moldability ⊚ ⊚ ⊚ ◯ ⊚ [Slush molded product physical properties]Tensile strength (MPa) 11.0 11.3 16.4 6.8 10.9 Elongation at break (%)400 420 370 490 300 Hardness (JIS-A) 65 65 94 35 81

TABLE 3 Comparative Comparative Example 6 Example 7 Example 8 Example 1Example 2 [Thermoplastic polymer particles] Formulation (parts by mass)Triblock copolymer (f) 100 (g) 100 (d) 70 (d) 100 Methacrylic resinStyrene-based block copolymer 100 Acetyl tri(n-butyl) citrate 30 Complexdynamic viscosity η*(5) (Pa.s) <20 <20 <20 2128 3079 η*(50) (Pa.s) <20<20 <20 381 508 Newtonian viscosity index n <0.1 <0.1 <0.1 0.75 0.78Average particle diameter (μm) 200 420 400 410 450 Melt viscosity (Pa.s)9 4 12 —¹⁾ —¹⁾ Slush moldability ⊚ ⊚ ◯ X X [Slush molded productphysical properties] Tensile strength (MPa) 17 8 4.2 —¹⁾ —¹⁾ Elongationat break (%) 280 530 400 —¹⁾ —¹⁾ Hardness (JIS-A) 96 70 30 —¹⁾ —¹⁾¹⁾ Impossible to measure

1. A thermoplastic polymer powder comprising an acrylic block copolymer(I) wherein said acrylic block copolymer comprises at least one polymerblock (A) comprising structural units originating from an acrylic ester;and at least one polymer block bonded thereto and selected from polymerblocks (B) comprising structural units originating from a methacrylicester and polymer blocks (C) comprising structural units originatingfrom an acrylic ester different from that of the polymer block (A)wherein said thermoplastic polymer powder; has a complex dynamicviscosity η*(5) of 5.0×10³ Pa.s or less, the viscosity η*(5) beingmeasured under conditions of a temperature of 250° C. and an angularfrequency of 5 rad/sec; has a Newtonian viscosity index n of 0.50 orless, the Newtonian viscosity index n being represented by the followingequation (1):n=log η*(5)-log η*(50)   (1) wherein n represents the Newtonianviscosity index, η*(5) represents the complex dynamic viscosity (unit:Pa.s) measured under conditions of a temperature 250° C. and an angularfrequency of 5 rad/sec, and η*(50) represents the complex dynamicviscosity (unit: Pa.s) measured under conditions of a temperature of250° C. and an angular frequency of 50 rad/sec; and has an averageparticle diameter of 1 mm or less.
 2. The thermoplastic polymer powderaccording to claim 1, wherein the melt viscosity measured with a rotaryviscometer at 250° C. and a shear rate of 0.2 sec⁻¹ is 3000 Pa.s orless.
 3. The thermoplastic polymer powder according to claim 1, which isobtained by an underwater cutting process or a shock pulverizingprocess.
 4. The thermoplastic polymer powder according to claim 1,wherein the weight average molecular weight of the acrylic blockcopolymer (I) is from 5,000 to 200,000.
 5. The thermoplastic polymerpowder according to claim 1, wherein the weight average molecular weightof the polymer block (A) constituting the acrylic block copolymer (I) isfrom 1,000 to 150,000, and the weight average molecular weights of thepolymer block (B) and the polymer block (C) are from 2,000 to 50,000. 6.The thermoplastic polymer powder according to claim 1, wherein theacrylic block copolymer (I) is a triblock copolymer made of the polymerblock (B)-the polymer block (A)-the polymer block (B).
 7. Thethermoplastic polymer powder according to claim 1, wherein thedifference between the solubility parameter σ(A) (unit: MPa^(1/2)) ofthe starting monomer(s) constituting the polymer block(s) (A) and thesolubility parameter σ(B) or σ(C) (unit: MPa^(1/2)) of the startingmonomer(s) constituting the polymer block (B) or the polymer block (C)is 2.5 or less.
 8. The thermoplastic polymer powder according to claim1, which is for slush molding or rotational molding.
 9. A processcomprising producing a molded product by performing slush molding orrotational molding with the thermoplastic polymer powder according toclaim
 1. 10. A molded product produced with the thermoplastic polymerpowder according to claim
 1. 11. The molded product according to claim10, which is a toy member having a JIS-A hardness of 40 to
 95. 12. Themolded product according to claim 10, which is a lighting cover having aJIS-A hardness of 95 or more.